1. Field of the Invention
The present invention relates to a method of manufacturing glass parts for connection of optical fibers, method of manufacturing mother glass to produce glass parts, and glass parts for connection of optical fibers.
2. Prior Art
Generally, in optical communication systems and optical applied equipment, optical connectors are used to connect optical fibers or connect an optical fiber and a light emitting/receiving device or the like.
Conventionally, optical connectors of this kind are divided into a split type as disclosed in Japanese Patent (KOUHOU) No. 2788800 and an integral type as shown in cross section in FIG. 17.
The integral type optical connector shown in FIG. 17 is comprised of a cylindrical glass ferrule 10 having a through hole 11 with a small diameter formed therein along a longitudinal central axis thereof. Optical fibers 12 and 13 are held in the through hole 11 with end faces 14 thereof abutting against each other. A matching agent (epoxy adhesive agent or ultraviolet hardening resin) is filled between the end faces 14. The matching agent acts to match the refractive index between the optical fibers 12 and 13, as well as bond the optical fibers together. The through hole 11 is tapered at its opposite open ends 15 and 16, so as to facilitate insertion of the optical fibers 12 and 13 into the through hole 11. The matching agent or an adhesive agent is filled in the open ends 15 and 16, and in gaps between the wall of the through hole 11 and the optical fibers 11 and 12 in order to fix the optical fibers 12 and 13 inside the through hole 11.
The ferrule 10 constructed as above is manufactured by forming a mother glass having a similar cross section to that of the ferrule, forming a through hole in the mother glass by machining, then drawing the mother glass with a through hole thus formed while heating the same to obtain a drawn glass, and then cutting the drawn glass into a suitable length. In manufacturing the ferrule 10, the formation of the mother glass and the through hole may be performed by press molding.
The ferrule 10 which is manufactured in the above described manner requires to have dimensional tolerances of xc2x13-5 xcexcm of the cross-sectional size of the through hole 11, so as to locate the optical fibers with an accuracy of the order of light wavelength.
According to the conventional manufacturing method described above, sufficient dimensional accuracy of the cross-sectional size of the through hole 11 cannot be achieved because the ferrule 10 is formed by hot drawing a prepared mother glass. As a result, the optical fibers 12 and 13 cannot be smoothly inserted into the ferrule 10, nor held in place with accuracy.
Further, the process of forming a through hole in the mother glass to manufacture the ferrule 10 by machining or by press molding takes much time and labor to perform.
In addition, the conventional ferrule 10 is solely designed to make a connection between single optical fibers and cannot make a connection between groups of plural optical fibers
It is a first object of the present invention to provide a method of manufacturing glass parts for connection of optical fibers, which can improve the accuracy of the cross-sectional size of a through hole in the glass part.
It is a second object of the present invention to provide a method of manufacturing mother glass to produce glass parts for connection of optical fibers, which can easily form a through hole in the mother glass.
It is a third object of the present invention to provide glass parts for connection of optical fibers, which are suitable for making a connection between groups of plural optical fibers.
To attain the first object, the present invention provides a method of manufacturing a glass part for connection of optical fibers, the glass part having at least one through hole formed therein to hold optical fibers, comprising the steps of:
preparing a mother glass having a similar cross section to a desired cross section of the glass part; and
drawing the prepared mother glass while heating the same;
wherein the mother glass is made of a glass having a maximum devitrification speed of 100 xcexcm or less per minute.
Preferably, the mother glass is made of a glass having a maximum devitrification speed of 10 xcexcm or less per minute.
More preferably, the mother glass is made of a glass selected from the group consisting of soda lime silicate glass, low alkali silicate glass, and germanate glass.
To attain the second object, the present invention provides a method of manufacturing mother glass to produce glass parts for connection of optical fibers, comprising the steps of:
putting together a plurality of glass elements having a polygonal cross section so as to form a through hole having a polygonal cross section; and
bonding together the glass elements put together by heat fusion.
Preferably, the glass elements comprises a number of glass elements equal to a number of sides of said polygonal cross section.
To attain the third object, the present invention provides a glass part for connection of optical fibers having at least one through hole formed therein to hold optical fibers, wherein the through hole has a cross section of a shape selected from the group consisting of polygon, oblong, ellipse, connected circles, and connected squares.
In a preferred embodiment, the through hole has a cross section of a shape selected from the group consisting of hexagon, octagon, and connected squares.
In another preferred embodiment, the through hole has a cross section of a shape selected from the group consisting of oblong, connected circles, and ellipse.
Preferably, the glass part is made of a glass having a maximum devitrification speed of 100 xcexcm or less per minute.
More preferably, the glass part is made of a glass having a maximum devitrification speed of 10 xcexcm or less per minute.
Further preferably, the glass part is made of a glass having approximately the same coefficient of linear expansion as that of optical fibers to be connected.
In another preferred embodiment, the glass part for connection of optical fibers has a through hole formed therein to hold optical fibers, wherein the through hole comprises a plurality of through holes.
The term xe2x80x9ccross sectionxe2x80x9d used throughout the present specification refers to a sectional form perpendicular to the direction in which the mother glass is drawn.